Significance of Advanced Cuttings Evaluation (ACE) Technologies for Chemostratigraphy Purposes While Drilling; Technology Overview & Applications

Abstract

Mud loggers are the first (and sadly in some cases the only) people to look at the cuttings. To actually see what the rocks look like, feel like, occasionally even taste. Most people looking at a well will actually look at "wriggly lines" or at best the cuttings descriptions from the loggers or geologist, two or three lines of abbreviations "claystone, light grey to grey, soft to firm, occasionally hard, slightly calcareous, trace fine sand". We have all read them, many of us have written them. These descriptions are incredibly useful and valuable, they are often all we have to understand the actual rocks and geology, especially with older wells. But in a world where we now enter the description and draw the logs with a computer, this information still comes from the subjective view of the logging geologist peering through a microscope In recent years, several tools have been developed to analyze drill cuttings from oil and gas wells. The most commonly used tools include X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDX), bulk density, and pyrolysis. Although each of these tools can be used to develop a limited determination of the in-situ rock character, the combination of three of these tools (XRF, SEM/EDX, and pyrolysis) can provide a more comprehensive picture of formation properties.The combination of XRF analysis with the SEM/EDX analysis is the key to the cuttings workflow. The exact location within the borehole can be determined and a robust mineralogy developed that is independent of normative mineralogy (typical XRF) or operator-interpretive mineralogy (XRD). Additional outputs include relative brittleness index, bulk density, lithology, fractional and textural relationships, total organic carbon (TOC) proxy, and a new porosity index. Trace and major elemental ratios are also available for precise stratigraphic placement. The addition of cuttings pyrolysis enables hydrocarbon typing, producible hydrocarbons, TOC, and total inorganic carbon (TIC) within each sample to be established.Chemical Lithostratigraphy uses whole rock inorganic geochemical (elemental) data, to give information on: Extrabasinal source area dominance and origin (volcanic, metamorphics, igneous, sedimentary), Extrabasinal component weathering or diagenesis (cementation) Intrabasinal components (Palaeoenvironment and insitu origin of sediments) Chemical Lithostratigraphy analysis of cuttings can be done application of automated mineralogical analysis of cuttings samples pre-drilling in defining stratigratic zones via mineralogy/elemental data. And then explore the application of the same data to assist, and in this case lead, the decision making process during directional drilling of the lateral well. The paper will also look at the use of the technology in defining tactical fracc-ing zone based on rock properties (e.g. ductility) determined from the mineralogical, elemental and textural data.This paper will show that through the use of automat...

Analysis of Cuttings’ Minerals for Multistage Hydraulic Fracturing Optimization in Volcanic Rocks

“…The application of elemental-mineral transformation analysis is a comprehensive technology used in geology. − The rock cutting analysis technology (RoqScan cuttings’ analysis system) , that is based on elemental-mineral transformation has been proposed by the CGG company from the United States. This technology provides the possibility of analysis while drilling. − Using this technology, field tests have been successfully implemented in various oil fields around the world, such as Bakken Shale, , Barnett Shale, Haynesville Shale in Northwest Louisiana, Southern Powder River Basin in Wyoming, Marcellus Shale, and Cauvery Basin in Southern India …”